Correct RealESRGAN expected architecture type to ESRGAN

[akx]

Description

Sibling of #14473. Spandrel seems to group all ESRGAN-style models under the ESRGAN architecture category:

spandrel\architectures\RealESRGAN is for anyone using spandrel to init their own models if they want to use the realesrgan version of the arch
internally they all they converted to original esrgan's key structure when loaded

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests